Exposure device for manufacturing colour picture tubes

ABSTRACT

In an exposure device for manufacturing a colour picture tube of the type comprising a source of light, and a correction lens having an effective surface divided into a plurality of discontinuous regions surrounded by boundary lines and disposed between the panel of the tube and the source of light whereby the photosensitive film coated on the inner surface of the panel is exposed to the light emanating from the source and transmitted through the correction lens to form a fluorescent screen, there is provided means for the correction lens for restricting the light transmitted through the discontinuous regions thereby uniformly exposing the photosensitive film.

United States Patent [1 1 Yamazaki et a1.

[ EXPOSURE DEVICE FOR MANUFACTURING COLOUR PICTURE TUBES [75] Inventors:Eiich Yamazaki, Ichihara; Koichi Maruyama; Toshio Ueda, both of Mobara,all of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Mar.2, 1972 21 Appl. No.: 231,313

[30] Foreign Application Priority Data Mar. 5, 1971 Japan 46/11274 [51]Int. Cl. G03b 27/16 [58] Field of Search 95/1 [56] References CitedUNITED STATES PATENTS Ramberg 95/1 Jan. 29, 1974 2,568,448 9/1951 Hansen..95/1 3,601,018 8/1971 Lange 95/1 Primary ExaminerJohn M. HoranAttorney, Agent, or Firm-Charles E. Pfund, Esq.; Chittick, Thompson &Pfund 5 7] ABSTRACT In an exposure device for manufacturing a colourpicture tube of the type comprising a source of light, and a correctionlens having an effective surface divided into a plurality ofdiscontinuous regions surrounded by boundary lines and disposed betweenthe panel of the tube and the source of light whereby the photosensitivefilm coated on the inner surface of the panel is exposed to the lightemanating from the source and transmitted through the correction lens toform a fluorescent screen, there is provided means for the correctionlens for restricting the light transmitted through the discontinuousregions thereby uniformly exposing the photosensitive film.

7 Claims, 6 Drawing Figures PATENTEU 3.788200 SHEEI 1 OF 3 PBIHHART 23 1PATENTED 3.788.200

sum 2 OF 3 F/ G 3 PRIOR ART PATENTEU 3,788,200

SHEET 3 0F 3 EXPOSURE DEVICE FOR MANUFACTURING COLOUR PICTURE TUBESBACKGROUND OF THE INVENTION This invention relates to an exposure deviceutilized to form a fluorescent screen of a colour picture tube and moreparticularly to an improved correction lens system.

Generally the fluorescent screen of a colour picture tube ismanufactured by applying in a regular pattern a plurality of trios ofphosphor dots of three colours on the inner surface of the face plate orpanel of the tube by photographic technique.

When forming the phosphor dots by photographic technique a correctionlens having an extremely complicated curved surface is used for thepurpose of causing the locus of the exposure light emanating from asource of light to approximate the locus of the electron beam prevailingin the completed tube.

As most of the conventional correction lenses have a continuously curvedsurface, with such lenses it has been impossible to perfectlyapproximate the locus of the exposure light with that of the electronbeam. For this reason, it has been impossible to perfectly approximatethe phosphor dots and the electron beam spots over the entire innersurface of the panel. As a consequence, the colour picture tube having afluorescent screen formed with such a correction lens having acontinuously curved surface has an inherent drawback of accompanying theproblem of colour shading and hence poor quality of the reproducedpicture.

To solve this problem, an improved correction lens has been proposed.FIG. 1 of the accompanying drawings shows a plan view of such acorrection lens, FIG. 2 the cross-section thereof and FIG. 3 the panelhaving a fluorescent screen formed with the correction lens shown inFIGS. 1 and 2 and viewed from the exterior of the tube.

As shown by FIG. 1, the upper or effective surface of the correctionlens is divided into a plurality of small rectangular regions 3partitioned by grid shaped boundary lines 2. As shown in FIG. 2, thesurface of each region is a flat or slightly curved surface inclined tothe bottom surface of the lens 1 so that the upper or effective surfaceof the lens is a discontinuous surface and the boundary lines 2 or theportions interconnecting adjacent regions form steep vertical sidesurfaces. Since the flat or slightly curved surfaces and the verticalside surfaces manifest different transmission characteristics to thelight transmitting through the correction lens, (boundary lines havesmaller transmissibility than the rectangular regions) the fluorescentscreen formed on the panel 4 with this correction lens has portions 5corresponding to flat regions 3 and grid shaped portions 6 correspondingto boundary lines 2, portions 5 and 6 having been exposed to light ofdifferent intensities. Such grid shaped pattern caused by non-uniformexposure is seen from outside of the tube whether it is operating ornot, thus degrading the quality of the re- 7 produced picture.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved exposure device capable of uniformly exposing thephotensensitive film coated on the inner surface of the panel of acolour picture tube thereby providing a colour picture tube capable ofreproducing pictures of excellent quality even when the photosensitivefilm is exposed to the light transmitting through a correction lenshaving a surface divided into a plurality of regions by means ofboundary lines having smaller transmissibility than the divided regions.

According to this invention there is provided an exposure device formanufacturing a colour picture tube of the type comprising a source oflight and a correction lens having an effective surface divided into aplurality of discontinuous regions surrounded by boundary lines anddisposed between the panel of the tube and the source of light wherebythe photosensitive film coated on the inner surface of the panel isexposed to the light emanating from the source and transmitted throughthe correction lens to form the dot pattern of a fluorescent screen,characterized in that means is associated with the correction lens forrestricting the light transmitted through the discontinuous regionsthereby uniformly exposing the photosensitive film.

The means for restricting the light may be comprised by a check patternof opaque substance applied on the discontinuous regions of thecorrection lens or on the surface of a transparent substrate combinedwith the correction lens.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings;

FIG. 1 shows a plan view of a prior art correction lens utilized in theexposure device;

FIG. 2 shows a cross-sectional view of the correction lens shown in FIG.1 taken along a line II II;

FIG. 3 shows a front view of the panel of a colour picture tube having afluorescent screen formed by using the correction lens shown in FIGS. 1and 2;

FIG. 4 shows a longitudinal sectional view of one example of theexposure device embodying the invention;

FIG. 5 is a plan view of a correction lens utilized in the exposuredevice shown in FIG. 4 and FIG. 6 shows a plan view of a filter utilizedin a modi- 3 fied exposure device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 shows one example of theexposure device 11 embodying the invention. As shown, the exposuredevice 11 comprises asource of light 12, and a correction lens 13utilized for the purpose of causing the locus of the light emanatingfrom the source of light 12 and transmitted through the correction lens13 to approximate the locus of the scanning electron beam of thecompleted colour picture tube. The panel 15' of the tube provided with ashadow mask 14 is mounted on the upper end of the exposure device 11.The inner surface of the panel 15 is coated with photosensitive filmwhich is exposed to the light emanating from the source of light andtransmitting through the correction lens 13 and the shadow mask 14 so asto form the dot pattern of a fluorescent screen of a prescribed pattern.

In accordance with this invention, in addition to the boundary lines 16which correspond to the boundary lines 2 shown in FIG. I, there areformed a plurality of lines 17 of opaque substance which are drawnhorizontally and vertically in parallel with the grid shaped boundarylines 16. Thus, an opaque grid shaped pattern is distributed uniformlyover the effective surface of the correction lens.

When the photosensitive film coated on the inner surface of the panel isexposed to the light transmitted through regions 18 of this improvedcorrection lens, the dark portions formed by the opaque lines 17 on thecorrection lens 13 and the dark portions formed by the boundary lines 16between the divided rectangular regions will be distributed uniformlyacross the entire area of the exposed photosensitive film, thus mak--ing substantially uniform the intensity of the exposure light. Thus, itis possible to eliminate dark stripes corresponding to the dark boundarylines of the prior art correction lens shown in FIG. 3. In this manner,with the exposure device of this invention it is possible to uniformlyexpose the photosensitive on the panel thereby producing a colourpicture tube of uniform appearance and capable of reproducing picturesof excellent quality.

FIG. 6 shows a plan view of a filter l9 utilized in a modifiedembodiment of this invention. The filter 19 comprises a transparentsubstrate of glass or the like on which are applied a plurality oflongitudinal and transverse lines 20 of opaque substance which intersectat right angles to form a check pattern. The filter is combined with theconventional correction lens shown in FlGS. 1 and 2 to form a correctionlens system which is used to expose the photosensitive film coated onthe inner surface of the panelult will be clear that this correctionlens system operates in the same manner as the correction lens shown inFIG. 5.

Although in the foregoing embodiments the check patterns were formed byapplying a plurality of longitudinal and transverse lines of opaquesubstance on the surface of the correction lens or filter, it should beunderstood that the same object can also be accomplished by formingstraight lines that restrict transmission of light on the surface of thecorrection lens or filter as by applying lines of translucent substanceor cutting straight grooves in the form of a check pattern.

As above described, the invention provides an improved exposure devicethat can uniformly expose the photosensitive film on the face plate ofacolour picture tube thereby reproducing pictures of excellent quality.

Although the invention has been shown and described in terms of somepreferred embodiments thereof it will be clear that many changes andmodifications will be obvious to one skilled in the art withoutdeparting from the true spirit and scope of the invention as defined inthe appended claims.

What is claimed is:

1. In an exposure device for manufacturing a colour picture tube of thetype comprising a source of light, and a correction lens having aneffective surface divided by boundary lines in the form of steep surfacediscontinuities into a plurality of discontinuous regions surrounded bysaid boundary lines, said lens disposed between the panel of said tubeand said source of light whereby the photosensitive film coated on theinner surface of said panel is exposed to the light emanating from saidsource and transmitted through said correction lens to form the dotpattern of a fluorescent screen, the improvement which comprises linemeans associated with said correction lens and positioned on oppositesides of each of said boundary lines and spaced therefrom for restricingthe light transmitted through said discontinuous region to therebysubstantially uniformly expose said photosensitive film.

2. The exposure device according to claim 1 wherein the surface of saidcorrective lens is divided into a plurality of rectangular regions bymeans of grid shaped boundary lines having smaller lighttransmissibility than said rectangular regionsand wherein said linemeans comprises a check pattern displaced from said grid shaped boundarylines.

3. The exposure device according to claim 2 wherein said check patterncomprises a plurality of lines of opaque substance applied on thesurface of said rectangular regions and intersecting each other at rightangles in said regions.

4. The exposure device according to claim 2 wherein said check patterncomprises a plurality of straight grooves formed on the surface of saidrectangular regions and intersecting each other at right angles in saidregions.

5. The exposure device according to claim 2 wherein said linemeans'comprises a filter combined with said correction lens, said filterincluding a transparent substrate and said check pattern formed andpositioned on said transparent substrate for restricting the lighttransmitted through said transparent substrate and through saidrectangular regions of said correction lens.

6. The exposure device according to claim 5 wherein said check patterncomprises a plurality of lines of opaque substance applied on thesurface of said subtersecting each other at right angles.

'Invmit'mfs) rm 3,788,200 ele mziezaelauw Eiichi Yamazaki, KoichiMaruyama,

Toshio Ueda It certified that error appears in the above-ixh-nti[icdpnu'nt; and LlmL said IAJLLUI'SQ InLont are hereby (:or'rvctvd as;slum-m below:

In"[75] Inventoirsz" 'correct the spelling of the name "Eiich" to EiichiColumn 1, line 66, "photensensitive" should be I photosensitive v Column3, line 14, after "photosensitive" insert film Column 4, line 15,"region" should be fegions Signed and sealed this 24th day of September-1974.

(SEAL) Attest:

McCOY M. GIBSON JR. Attesting Officer c; MARSHALL DANN Comipnioner ofPatents UNI'I I'II) S'i'A'll'lh' I)\'IF.N'I (I|-'l"| (".l". (T RUTH"! 1A'Il") 0 F (H ii R FICTION Patent :10. 3,788,200- "D t ,Ja ary ggbli'lgEiichi Ya'mazaki', Koichi Mar uy'ama, -.[nlfhtur(1:) Toshlo Ueda It mmfiml that error appears i.n the ahove.1'x h-nt.li[iorl patent;

' and LhuL smid LL-Ltm'sz lnLent; are hereby corrvcu-d as; szhuwn below:

In"[.75] Inventors:- l'corr ect the spelling of (me name "Eiich" toEiichi V Column l,v line 66, "photensensitive" should bephotosensifiifrem v Column 3, line 14, after "photosensitive" insert' film 5 Col'umh 4, line'l5, ."r e gior i" should b qions si hed and sealedthiafl sth' day saw-emu 1974.

(SEAL) Attest:

McCOY M. GIBSON JR." Attesting Officer 0." mum Commissioner of Patents

1. In an exposure device for manufacturing a colour picture tube of thetype comprising a source of light, and a correction lens having aneffective surface divided by boundary lines in the form of steep surfacediscontinuities into a plurality of discontinuous regions surrounded bysaid boundary lines, said lens disposed between the panel of said tubeand said source of light whereby the photosensitive film coated on theinner surface of said panel is exposed to the light emanating from saidsource and transmitted through said correction lens to form the dotpattern of a fluorescent screen, the improvement which comprises linemeans associated with said correction lens and positioned on oppositesides of each of said boundary lines and spaced therefrom for restricingthe light transmitted through said discontinuous region to therebysubstantially uniformly expose said photosensitive film.
 2. The exposuredevice according to claim 1 wherein the surface of said corrective lensis divided into a plurality of rectangular regions by means of gridshaped boundary lines having smaller light transmissibility than saidrectangular regions and wherein said line means comprises a checkpattern displaced from said grid shaped boundary lines.
 3. The exposuredevice according to claim 2 wherein said check pattern comprises aplurality of lines of opaque substance applied on the surface of saidrectangular regions and intersecting each other at right angles in saidregions.
 4. The exposure device according to claim 2 wherein said checkpattern comprises a plurality of straight grooves formed on the surfaceof said rectangular regions and intersecting each other at right anglesin said regions.
 5. The exposure device according to claim 2 whereinsaid line means comprises a filter combined with said cOrrection lens,said filter including a transparent substrate and said check patternformed and positioned on said transparent substrate for restricting thelight transmitted through said transparent substrate and through saidrectangular regions of said correction lens.
 6. The exposure deviceaccording to claim 5 wherein said check pattern comprises a plurality oflines of opaque substance applied on the surface of said substrate andintersecting each other at right angles.
 7. The exposure deviceaccording to claim 5 wherein said check pattern comprises a plurality ofstraight grooves formed on the surface of said substrate andintersecting each other at right angles.